selective transmission

A space-time-frequency ( STF) coded orthogonal frequency division multiplexing ( OFDM) transmitter diversity scheme for fast fading frequency selective channels is proposed. The proposed STF-OFDM transmission scheme owns time diversity gain.

提出了一种基于空间时间频率（STF）编码的正交频分多路复用（OFDM）发射分集方案，这种传输方案可用于频率选择性快衰落信道。

And the other is how to cope with more severe channels fading, such as frequency selective fading and time selective fading to improve the transmission quality of signals in the high speed communication, which is also very difficult task.

其二，在高速通信的环境中，信道的衰落干扰问题更加严重，如频率选择性衰落和时间选择性衰落。怎样克服衰落的影响，提高信号的传输质量，同样是一个难题。

However, poor conditions of transmission, serious noise background, time and frequency selective fading, the limited bandwidth of channel result in serious distortion of UWA communication signals.

但由于水声通信传输条件恶劣，存在严重的噪声背景，并且水下声信道的带宽十分有限，再加上复杂的多径传播和时间、频率选择性衰落，导致水声通信信号严重畸变。

The superficial layers are often frequency selective to transmission.

表层传播一般都有频率选择性.

Based on Lambert Law, the regulation on infrared transmission properties of plain cloth and its moisture content is studied by using infrared heat effect and selective absorption function of moisture to infrared ray.

以朗伯（Lambert）定律为基础，利用红外线的热效应和水分对红外线的选择性吸收作用，研究了平纹织物含水量对红外线透射性能的影响。